Field Guide to Optical Lithography
Field Guide to Optical Lithography
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光学光刻现场指南
DOI：
10.1117/3.665802
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
C. Mack
中科院分区：
文献类型：
--
作者：
C. Mack
相移掩模相移掩模（PSM）的工作原理是在掩模中添加相位信息和振幅信息。二元铬-玻璃掩模使用Chrome（具有零幅度透射率）和玻璃（具有100%幅度透射率）对关于在何处定位抗蚀剂边缘的信息进行编码。相移掩模依赖于这样的事实，即通过透明介质的光将经历作为其光学厚度（折射率乘以物理厚度）的函数的相变。因此，穿过一定厚度的石英的光将具有与穿过相同厚度的空气的光不同的相位透射率。通过调整石英的厚度，可以获得任意相位差，将相移设置为180，可以获得焦深良好的高分辨率成像。来自掩模的移位和未移位部分的光在组合时将由于180 °相移而在图像平面处干涉和抵消。如果移动的光和未移动的光是等量的，则消除将完成。相移掩模掩模上0-180的相位边缘将打印为窄的暗线。这些边缘的阵列将打印宽度低至0.25 λ/NA的线和间隔的图案。PSM的常见类型是交替的（如图所示）和衰减的PSM。PSM的实际实现受到相位终止问题和掩模制造困难的限制。
Phase-Shift Masks Phase-shift masks (PSMs) work by adding phase information to the mask in addition to amplitude information. A binary chrome-on-glass mask encodes the information about where to position resist edges using chrome (with zero amplitude transmittance) and glass (with 100% amplitude transmittance). A phase-shift mask relies on the fact that light passing through a transparent media will undergo a phase change as a function of its optical thickness, the refractive index times the physical thickness. Thus, light passing through a certain thickness of quartz will have a different phase transmittance than light passing through the same thickness of air. By adjusting the thickness of the quartz, any phase difference can be obtained.By setting the phase shift to be 180, high-resolution imaging with good depth of focus can be obtained. Light from shifted and unshifted parts of the mask, when combined, will interfere and cancel out at the image plane due to the 180 phase shift. If the shifted and unshifted light is of equal quantity the cancellation will be complete. Phase-Shift Masks A 0–180 phase edge on a mask will print as a narrow dark line. An array of these edges will print patterns of lines and spaces with widths as low as 0.25 λ/NA. Common types of PSMs are alternating (pictured here) and attenuated PSMs. Practical implementation of PSMs is limited by phase termination problems and mask fabrication difficulties.